4 myths about cancer nutrition debunked

Being diagnosed with cancer can be an extremely difficult time that can lead to numerous psychological, emotional, and physical issues both for patients and their families or carers. Cancer treatment is multifactorial and the need for proper nutrition is inevitable since it can alleviate the side effects of the medical treatment, and maintain healthy body weight and strength. However, it is vital for every cancer patient or carer to see a dietitian to discuss the right choices for the particular case and make an individualised patient-centred plan.


There are two main different types of oncology-specific diets: complementary diet and alternative diet. The first one is usually used along with the medical treatment- either to alleviate symptoms or side effects of the treatment. The second one is used to replace medical treatment (although in most cases this is not preferable).

There is a lot of wrongful information and recommendations on the internet. The aim of this article is to outline the main myths about cancer nutrition.

Myth 1: Dairy should be avoided 

Some people believe that hormones utilised in the production of milk and dairy products may be linked to cancerous tumour growth. However, there is no clear relation between dairy consumption and the risk of cancer due to hormones.

There is even some evidence that dairy can have a protective role in the progression of breast cancer since it contains calcium, vitamin D, butyrate linoleic acid and lactoferrin (Dong et al. 2011).

Myth 2: Soy should be avoided

Isoflavones, which are normally found in soy products, have a similar structure to oestrogen that is found to promote some cancerous tissue growth. Thus, some researchers suppose foods that contain soy may have a similar effect.

However, current evidence shows that isoflavones are safe to consume when they appear naturally in foods and soya-based products and foods can be part of a healthy and balanced diet, especially when one wants to focus on non-meat protein sources that also provide some fibre (Cancer Research UK 2022). 

Myth 3: Sugar feeds cancer

Sugar is a very broad term. It can be white sugar or fructose which is the sugar in fruits. Thus, sugars are found in many healthy foods such as complex carbohydrates, fruits and vegetables, which are rich in dietary fibre, vitamins and minerals - all linked to decreased risk of cancer incidence. When eliminating sugar from the diet, this does not necessarily restrict glucose (sugar) to feed cancer cells (AICR 2016). 

However, bear in mind that excessive sugar is recommended to be limited, especially ‘free’/’simple’ sugars like those found in sugary drinks which are all related to weight gain.

Myth 4: Alkaline environment is beneficial

Some people claim that an acidic environment may promote ill health when compared to an alkaline environment. The food we consume can affect the body’s pH and, since our blood is alkaline, acidic foods may upset the body’s balance. But no consensus on this has been made (AICR 2010).

The fact is that the pH of the blood is regulated by the kidneys and the respiratory system, and any excess acids would be excreted in the urine. Moreover, cancer cells as well as healthy cells cannot survive in an alkaline environment. Therefore, no research can establish the beneficial effect of such a diet (AICR 2010).

It is important to know that every type of cancer is different. It affects different parts of the body, which is why the treatment differs as well as the nutritional recommendations. Sometimes, the only beneficial thing is to prevent malnutrition in oncology patients, which is hard enough for the patients themselves.

Thus, it is vital to have an appointment with a relevant healthcare practitioner (such as a dietitian) to assess the health status and needs of the individual before any advice is given.


DONG, J. et al., 2011. Dairy Consumption and risk of breast cancer: a meta-analysis of protective cohort studies. Breast Cancer Research and Treatment, 127(1), pp. 23-31. 

AMERICAN INSTITUTE FOR CANCER RESEARCH (AICR), 2010. The Alkaline Diet: Another Cancer and Diet Claim. [online]. US: AICR. Available from: The Alkaline Diet and Cancer - American Institute for Cancer Research % (aicr.org)[Accessed 20 January 2023].

AMERICAN INSTITUTE FOR CANCER RESEARCH (AICR), 2016. The Sugar and Cancer Connection. [online]. US: AICR. Available from: The Sugar and Cancer Connection - American Institute for Cancer Research (aicr.org) [Accessed 20 January 2023].

CANCER RESEARCH UK, 2022. Food myths and cancer. [online]. UK: Cancer Research UK. Available from: Food Myths | Health Myths and Facts | Cancer Research UK[Accessed 20 January 2023].

The views expressed in this article are those of the author. All articles published on Nutritionist Resource are reviewed by our editorial team.

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Aberdeen, UK, AB25
Written by Kristina Vavura, Registered Dietitian (RD) and Clinical Data Manager (CDM)
Aberdeen, UK, AB25

I am a registered dietitian (RD) in the UK and Bulgaria and a Clinical Data Manager (CDM) in Bayer. I have experience in creating nutritional regimens for overweight and obese patients, type 1 and type 2 diabetes, malnutrition, dyslipidaemia, cholelithiasis, nephrolithiasis and many other diseases. I also provide nutritional guidance for patients.

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